1. Field of the Invention
The present invention relates to an optical module used in an optical communication system, and a method of manufacturing the same.
An optical module provides a parallel beam of light which is emitted from a light emitting element through an optical lens and converged at a focal point of the lens at which an optical fiber is located, and such an optical module must be subjected to various environmental tests of the quality and reliability thereof.
2. Description of the Related Art
FIG. 9 shows a known optical module in which a light emitting element 1 is supported on a substrate (carrier) 7 and outputs light to an optical fiber 2 supported by a ferrule 9, through a converging lens 3 or a lens unit having a converging lens 3. The ferrule 9 of the optical fiber 3 is inserted and supported in a support 11 having a glass window 4, which defines an air-sealed chamber in a housing 5 of the module to isolate the light emitting element 1 from the environment. The substrate 7 and the support 11 are secured to the housing 5, and the lens 3 is supported by a lens holder 6 immovably supported by the substrate 7.
The light emitted from the light emitting element 1 is converged onto the focal point of the converging lens 3 to be incident on the optical fiber 2, whereby an optical connection is established between the light emitting element 1 and the optical fiber 2.
To converge the light emitted from the light emitting element 1 and incident on the front end of the optical fiber 1, through the converging lens 3, the position of the lens 3 must be precisely adjusted. To allow this adjustment to be made, first the lens 3 is immovably soldered to or press-fitted in a lens insertion hole 12 (FIGS. 10 and 11) of the lens holder 6, the lens holder 6 is then moved up and down and right and left with respect to the substrate 7 by an adjusting tool or jig or the like (not shown) to adjust the position of the lens 3, and after the adjustment is completed, the lens holder 6 is secured to the substrate 7 by an adhesive or solder 10, as shown in FIGS. 10 and 11.
In the conventional optical module as shown in FIGS. 9, 10, and 11, the center of the lens insertion hole 12 is offset from the center of the lens holder 6 toward the bottom of the lens holder 6 facing the upper surface of the substrate 7, to allow for any necessary downward movement of the lens holder 6 during the adjustment of the position of the lens 3, and thus, usually, a slight clearance remains between the bottom of the lens holder 6 and the substrate 7 after the adjustment is completed. This clearance is filled with the solder (or adhesive) 10.
Consequently, even though the lens holder 6, and accordingly the lens 3, are exactly positioned by the adjusting operation as mentioned above, an accidental and undesirable displacement or deviation of the lens 3 could occur due to a creep of the solder (or adhesive) 10 caused by a thermal stress during the environmental tests, to thereby cause a misalignment of the optical connection.